Image decoding method, image coding method, image decoding apparatus, image coding apparatus, and image coding and decoding apparatus

ABSTRACT

An image decoding method of decoding, on a block-by-block basis, image data included in a coded stream includes: deriving candidates for an intra prediction mode to be used for intra prediction for a decoding target block, the number of the candidates constantly being a plural number; obtaining, from the coded stream, an index for identifying one of the derived candidates for the intra prediction mode; and determining, based on the obtained index, one of the derived candidates for the intra prediction mode as the intra prediction mode to be used for intra prediction for the decoding target block.

TECHNICAL FIELD

The present disclosure relates to moving picture decoding methods andmoving picture coding methods, and in particular, to methods of decodingand coding mode information including intra prediction mode numbers usedfor generating prediction pixels.

BACKGROUND ART

In the High Efficiency Video Coding (HEVC) Standard that is one of thenext-generation image coding standards, various considerations forincreasing coding efficiency have been made (see Non-patent Literature1).

Examples of coding include inter frame coding and intra coding. In theinter frame coding, compression is performed by inter frame predictionwhere a prediction image is generated with reference to pixelinformation of a previous frame. In the intra coding, compression isperformed by intra prediction where a prediction image is generated withreference to pixel information within a picture.

In the intra coding, modes are prepared in number (intraPredModeNum)corresponding to the predetermined sizes of coding target blocks (thepredetermined sizes are, for example, the values of log 2TrafoSize andthe types of Prediction Units) in order to differentiate the directionsetc. for generating intra prediction pixels.

For example, it is currently considered to prepare 34 modes (the valueof intraPredModeNum is 34) for coding target blocks each having a valueof the size log 2TrafoSize within a range from 3 to 5 inclusive (FIG.15).

These modes are called intra prediction modes (IntraPredMode). The valueof the intra prediction mode (intra prediction mode number) is a valuethat represents a corresponding prediction direction. For example, thereare 34 or 17 intra prediction modes. For example, a value (or a label)“0” of the intra prediction mode number shows the vertical (direction),a value “1” of the intra prediction mode number shows the horizontal(direction), a value “2” of the intra prediction mode number shows nodirection called DC mode prediction, and values of 3 and larger (valuesbetween 3 and 33 inclusive for blocks having a predetermined size) ofthe intra prediction mode number show predetermined-angle directionsassociated respectively thereto.

Hereinafter, in this Description, the intra prediction mode numberassociated with a coding target block is referred to as a “target modenumber”. The value indicated by a code string obtained by coding the“target mode number” according to a predetermined coding scheme isreferred to as a “coding mode number” in order to differentiate from the“target mode number”.

For decoding a decoding target block (such as a luminance block), modeinformation is used which is “information for identifying which one ofintra prediction modes should be used”. The mode information isgenerated for each prediction unit (hereinafter, referred to as PU).

At present, it is currently considered that mode information includesthree information pieces as indicated below.

(I1) A “prediction mode use flag” (prev_intra_luma_pred_flag) that is aflag determining whether or not to use the value of intra predictionmode of an adjacent PU decoded before

(I2) A “candidate prediction mode number” (mpm_idx) that is an indexindicating, when there are two or more candidates for the intraprediction mode (hereinafter, referred to as candidate intra predictionmodes), which one of the candidate intra prediction modes should be usedFor example, the default index value is “0” which indicates the firstcandidate intra prediction mode.

(I3) A “coding mode number” (rem_intra_luma_pred_mode) that is a code(value) associated with a “target mode number” when the intra predictionmode number of an adjacent PU decoded before is not used In the decodingprocess, (1) the “coding mode number” is first extracted from the codestring included in the mode information according to a predeterminedvariable length decoding method etc. (arithmetic decoding method etc.),and (2) using the extracted value, the “target mode number” (any one ofthe aforementioned 34 modes from 0 to 33 inclusive) is derived (orinformation used for the derivation is derived).

CITATION LIST Non Patent Literature

-   Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3    and ISO/IEC JTC1/SC29/WG11 5th Meeting: Geneva, CH,—6-23 Mar. 2011    JCTVC-E603 Title: WD3: Working Draft 3 of High-Efficiency Video    Coding ver.5    http://phenix.int-evry.fr/jct/doc_end_user/documents/5_Geneva/wg    11/JCTVC-E603-v5.zip

SUMMARY OF INVENTION Technical Problem

However, in the conventional intra coding, the compression efficiency ofthe mode information is insufficient.

The present disclosure has been conceived to solve such a drawback andis aimed at providing an image coding method, an image coding apparatus,an image decoding method, an image decoding apparatus, and an imagecoding and decoding apparatus which compress mode information withhigher efficiency.

Solution to Problem

In order to solve the above drawback, an image decoding method accordingto an exemplary embodiment of the present disclosure is an imagedecoding method of decoding, on a block-by-block basis, image dataincluded in a coded stream. The image decoding method includes: derivingcandidates for an intra prediction mode to be used for intra predictionfor a decoding target block, the number of the candidates constantlybeing a plural number; obtaining, from the coded stream, an index foridentifying one of the derived candidates for the intra prediction mode;and determining, based on the obtained index, one of the derivedcandidates for the intra prediction mode as the intra prediction mode tobe used for intra prediction for the decoding target block.

In order to solve the above drawback, an image coding method accordingto an exemplary embodiment of the present disclosure is an image codingmethod of generating a coded stream by coding image data on ablock-by-block basis. The image coding method includes: derivingcandidates for an intra prediction mode to be used for intra predictionfor a decoding target block corresponding to a coding target block, thenumber of the candidates constantly being a plural number; determiningone of the derived candidates for the intra prediction mode as the intraprediction mode to be used for intra prediction for the decoding targetblock; and adding, to the coded stream, an index for identifying thedetermined one of the derived candidates for the intra prediction mode.

In order to solve the above drawback, an image decoding apparatusaccording to an exemplary embodiment of the present disclosure is animage decoding apparatus for decoding, on a block-by-block basis, imagedata included in a coded stream. The image decoding apparatus includes:a deriving unit configured to derive candidates for an intra predictionmode to be used for intra prediction for a decoding target block, thenumber of the candidates constantly being a plural number; an obtainingunit configured to obtain, from the coding stream, an index foridentifying one of the derived candidates for the intra prediction mode;and a determining unit configured to determine, based on the obtainedindex, one of the derived candidates for the intra prediction mode asthe intra prediction mode to be used for intra prediction for thedecoding target block.

In order to solve the above drawback, an image coding apparatusaccording to an exemplary embodiment of the present disclosure is animage coding apparatus for generating a coded stream by coding an imagedata on a block-by-block basis. The image coding apparatus includes: aderiving unit configured to derive candidates for an intra predictionmode to be used for intra prediction for a decoding target blockcorresponding to a coding target block, the number of the candidatesconstantly being a plural number; a determining unit configured todetermine one of the derived candidates for the intra prediction mode asthe intra prediction mode to be used for intra prediction for thedecoding target block; and an adding unit configured to add, to thecoding stream, an index for identifying the determined one of thederived candidates for the intra prediction mode.

In order to solve the above drawback, an image coding and decodingapparatus according to an exemplary embodiment of the present disclosureincludes: the image decoding apparatus; and the image coding apparatus.

These general and specific aspects may be implemented by using a system,a method, an integrated circuit, a computer program, a recording mediumor any combination of the system, method, integrated circuit, computerprogram, or recording medium.

Advantageous Effects of Invention

According to the present disclosure, it is possible to reduce theprocessing amount while maintaining coding efficiency.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present invention. In the Drawings:

FIG. 1 is a block diagram illustrating a configuration example of animage coding apparatus according to Embodiment 1;

FIG. 2 is a flowchart of a mode information generating method in animage coding method according to Embodiment 1;

FIG. 3 is a flowchart of a detail of Step S215 in FIG. 2;

FIG. 4 is a flowchart of a prediction mode determining method accordingto Embodiment 1;

FIG. 5 is a flowchart of an example of a method of coding a coding modenumber according to a CABAC scheme (Step S217);

FIG. 6A is a conceptual diagram illustrating an example of aconventional syntax structure;

FIG. 6B is a conceptual diagram illustrating an example of a syntaxstructure according to Embodiment 1;

FIG. 7 is a flowchart of a variation of the prediction mode determiningmethod according to Embodiment 1;

FIG. 8 is a flowchart of an example of another method of coding thecoding mode number (Step S217);

FIG. 9A is an example of a coding table used in the another method ofcoding the coding mode number (Step S217);

FIG. 9B is another example of the coding table used in the anothermethod of coding the coding mode number (Step S217);

FIG. 10 is a block diagram illustrating a configuration of a decodingapparatus 2 according to Embodiment 2;

FIG. 11 is a flowchart of a decoding method according to Embodiment 2;

FIG. 12A is a flowchart of an arithmetic decoding processing performedwhen a bit string is output according to the CABAC scheme;

FIG. 12B is a flowchart of the arithmetic decoding processing performedwhen a bit string is output according to the CAVLC scheme;

FIG. 13 is a flowchart of a detail of a first example of Step S1117;

FIG. 14 is a flowchart of a detail of Step S1115;

FIG. 15 is a conceptual diagram of an example of a decoding predictionmode;

FIG. 16 shows an overall configuration of a content providing system forimplementing content distribution services;

FIG. 17 shows an overall configuration of a digital broadcasting system;

FIG. 18 is a block diagram illustrating an example of a configuration ofa television;

FIG. 19 is a block diagram illustrating an example of a configuration ofan information reproducing/recording unit that reads and writesinformation from and on a recording medium that is an optical disk;

FIG. 20 shows an example of a configuration of a recording medium thatis an optical disk;

FIG. 21A shows an example of a cellular phone;

FIG. 21B is a block diagram showing an example of a configuration of acellular phone;

FIG. 22 illustrates a structure of multiplexed data;

FIG. 23 schematically shows how each stream is multiplexed inmultiplexed data;

FIG. 24 shows how a video stream is stored in a stream of PES packets inmore detail;

FIG. 25 shows a structure of TS packets and source packets in themultiplexed data;

FIG. 26 shows a data structure of a PMT;

FIG. 27 illustrates an internal structure of multiplexed datainformation;

FIG. 28 illustrates an internal structure of stream attributeinformation;

FIG. 29 shows steps for identifying video data;

FIG. 30 shows an example of a configuration of an integrated circuit forimplementing the moving picture coding method and the moving picturedecoding method according to each of embodiments;

FIG. 31 shows a configuration for switching between driving frequencies;

FIG. 32 shows steps for identifying video data and switching betweendriving frequencies;

FIG. 33 shows an example of a look-up table in which video datastandards are associated with driving frequencies;

FIG. 34A is a diagram showing an example of a configuration for sharinga module of a signal processing unit; and

FIG. 34B is a diagram showing another example of a configuration forsharing a module of the signal processing unit.

DESCRIPTION OF EMBODIMENTS

In order to solve the above drawback, an image decoding method accordingto an exemplary embodiment of the present disclosure is an imagedecoding method of decoding, on a block-by-block basis, image dataincluded in a coded stream. The image decoding method includes: derivingcandidates for an intra prediction mode to be used for intra predictionfor a decoding target block, the number of the candidates constantlybeing a plural number; obtaining, from the coded stream, an index foridentifying one of the derived candidates for the intra prediction mode;and determining, based on the obtained index, one of the derivedcandidates for the intra prediction mode as the intra prediction mode tobe used for intra prediction for the decoding target block.

The followings are three possible structures of the conventional modeinformation.

(M1) When one of the candidate intra prediction modes is used and thereare a plurality of candidate intra prediction modes (the value ofNumMPMCand is greater than 1), mode information includes the (I1)“prediction mode use flag” and the (I2)“candidate prediction modenumber”.

(M2) When the candidate intra prediction mode is used and there is onecandidate intra prediction mode, the mode information includes only the(I1) “prediction mode use flag”. This is because the target mode numberis uniquely identified when there is only one candidate intra predictionmode, thereby not requiring the (I2) “candidate prediction mode number”.Conventionally, the “candidate prediction mode number” is not includedwhen there is only one candidate intra prediction mode, to reduce theinformation amount of the mode information.

(M3) When no candidate intra prediction mode is used, the modeinformation includes the (I1) “prediction mode use flag” and the (I3)“coding mode number” obtained by coding the target mode number. Theinformation amount of the “coding mode number” is significantly greaterthan that of the (I2) “candidate prediction mode number” or the like.

In the image decoding method with the above configuration, two or morecandidates are constantly derived, resulting in the high rate of the PUswhich use the candidate intra prediction modes. In other words, it ispossible to reduce the information amount because the rate of the modeinformation (M2) having relatively smaller amount of informationincreases and the rate of the mode information (M3) having larger amountof information decreases. When the mode information corresponds to theconventional mode information (M1), the same information amount as thatof the mode information (M2) is necessary; and thus, when the modeinformation corresponds to the conventional mode information (M1), theinformation amount increases. However, the information amount of the(I2) “candidate prediction mode number” is significantly smaller thanthat of the (I3) “coding mode number”. As a result, the mount of reducedinformation is greater than the amount of increased information in anentire frame or an entire coding target block, leading to a reduction inthe amount of the mode information.

Furthermore, for example, it may be that the plural number is a fixednumber.

According to the image decoding method with the above configuration, thenumber of the candidate intra prediction modes to be derived is fixed totwo or more. As a result, when a candidate intra prediction mode isused, it is not necessary to perform a process for determining thenumber of candidate intra prediction modes.

The process for determining the number of candidate intra predictionmodes is, for example, a process for determining whether or not thenumber of candidate intra prediction modes indicated by the conditionalexpression 901 “if (NumMPMCand>1)” in FIG. 6A is 1. In the process, forexample, a process is necessary which is for obtaining the intraprediction mode numbers of the PUs to be referred to and determiningwhether or not the intra prediction mode numbers of the PUs match oneanother.

Here, the process for deriving the intra prediction mode numbers of thePUs to be referred to and the process for obtaining the intra predictionmode used for a decoding target block may be performed in parallel toincrease processing speed. Conventionally, when the (I1) “predictionmode use flag” indicates the use of the candidate intra prediction mode,a result of the process for deriving the intra prediction mode numbersof the PUs to be referred to needs to be obtained in order to determinewhether or not a coding stream includes an index. As a result, theprocess for obtaining the intra prediction mode used for a decodingtarget block cannot be performed till the result is obtained, whichresults in an insufficient increase of the processing speed.

On the other hand, according to the image decoding method with the aboveconfiguration, the fixed number that is two or more of the candidateprediction modes are constantly generated. As a result, the process fordetermining the number of candidate intra prediction modes is notnecessary, allowing the decoding of parameters at the decoding sideindependently of the number of prediction modes (the number ofcandidates). As a result, it is possible to perform the process forobtaining the intra prediction mode used for the decoding target blockwithout waiting for the result of the process for deriving the intraprediction mode numbers of the PUs to be referred to. It allows anincrease of the processing speed of an apparatus which executes theimage decoding method.

For example, it may be that the deriving includes: deriving a firstcandidate for the intra prediction mode to be used for intra predictionfor the decoding target block from an intra prediction mode used forintra prediction for each of adjacent blocks that are adjacent to thedecoding target block; determining whether or not the number of thederived first candidates is smaller than the plural number; and furtherderiving a second candidate for the intra prediction mode to be used forintra prediction for the decoding target block, when it is determinedthat the number of the derived first candidates is smaller than theplural number.

For example, it may also be that in the deriving of a first candidate,the number of the adjacent blocks for which the intra prediction modeused for intra prediction is obtained equals the plural number.

For example, it may also be that in the deriving of a second candidate,the second candidate is derived such that a total number of the firstcandidates and the second candidates equals the plural number.

For example, it may also be that in the deriving of a second candidate,an intra prediction mode different from the intra prediction mode usedfor intra prediction for each of the adjacent blocks that are adjacentto the decoding target block is derived as the second candidate.

For example, it may also be that in the deriving of a second candidate,at least one of (i) an intra prediction mode indicating prediction usinga mean value of pixel values of the decoding target block, (ii) an intraprediction mode indicating plane prediction, and (iii) an intraprediction mode indicating vertical prediction, is derived as the secondcandidate.

For example, it may also be that the coded stream includes a flagindicating whether to use one of the candidates for the intra predictionmode, when the flag indicates that one of the candidates for the intraprediction mode is used, (i) in the obtaining, the index is obtained,and (ii) in the determining, the one of the derived candidates isdetermined as the intra prediction mode to be used for intra predictionfor the decoding target block, and when the flag indicates that one ofthe candidates for the intra prediction mode is not used, (i) in theobtaining, a mode number is obtained from the coded stream, the modenumber indicating the intra prediction mode to be used for intraprediction for the decoding target block, and (ii) in the determining,the intra prediction mode to be used for intra prediction for thedecoding target block is determined based on the obtained mode number.

For example, it may also be that in the deriving, (i) when an adjacentblock that is adjacent to the decoding target block exists, an intraprediction mode other than the intra prediction mode used for intraprediction for the adjacent block is derived as the candidates for theintra prediction mode, and (ii) when the adjacent block that is adjacentto the decoding target block does not exist, the candidates for theintra prediction mode are derived based on a predetermined condition.

For example, it may also be that in the deriving, a candidate list isfurther generated using the candidates for the intra prediction mode,and the index is a number for identifying one of the candidates for theintra prediction mode included in the candidate list.

In order to solve the above drawback, an image coding method accordingto an exemplary embodiment of the present disclosure is an image codingmethod of generating a coded stream by coding image data on ablock-by-block basis. The image coding method includes: derivingcandidates for an intra prediction mode to be used for intra predictionfor a decoding target block corresponding to a coding target block, thenumber of the candidates constantly being a plural number; determiningone of the derived candidates for the intra prediction mode as the intraprediction mode to be used for intra prediction for the decoding targetblock; and adding, to the coded stream, an index for identifying thedetermined one of the derived candidates for the intra prediction mode.

For example, it may be that the plural number is a fixed number.

For example, it may also be that in the determining, a candidate whichmatches the intra prediction mode used for intra prediction for thecoding target block is determined as the one of the derived candidatesfor the intra prediction mode, the candidate being included in thederived candidates for the intra prediction mode.

In order to solve the above drawback, an image decoding apparatusaccording to an exemplary embodiment of the present disclosure is animage decoding apparatus for decoding, on a block-by-block basis, imagedata included in a coded stream. The image decoding apparatus includes:a deriving unit configured to derive candidates for an intra predictionmode to be used for intra prediction for a decoding target block, thenumber of the candidates constantly being a plural number; an obtainingunit configured to obtain, from the coding stream, an index foridentifying one of the derived candidates for the intra prediction mode;and a determining unit configured to determine, based on the obtainedindex, one of the derived candidates for the intra prediction mode asthe intra prediction mode to be used for intra prediction for thedecoding target block.

In order to solve the above drawback, an image coding apparatusaccording to an exemplary embodiment of the present disclosure is animage coding apparatus for generating a coded stream by coding an imagedata on a block-by-block basis. The image coding apparatus includes: aderiving unit configured to derive candidates for an intra predictionmode to be used for intra prediction for a decoding target blockcorresponding to a coding target block, the number of the candidatesconstantly being a plural number; a determining unit configured todetermine one of the derived candidates for the intra prediction mode asthe intra prediction mode to be used for intra prediction for thedecoding target block; and an adding unit configured to add, to thecoding stream, an index for identifying the determined one of thederived candidates for the intra prediction mode.

In order to solve the above drawback, an image coding and decodingapparatus according to an exemplary embodiment of the present disclosureincludes the image decoding apparatus; and the image coding apparatus.

A part or all of the constituent elements constituting the image codingapparatus and the image decoding apparatus may be configured from asingle system LSI (Large Scale Integration). The system LSI is asuper-multifunction LSI manufactured by integrating constitute units onone chip, and is specifically a computer system configured by includinga microprocessor, a ROM, a RAM (Random Access Memory), and so on.

Hereinafter, certain exemplary embodiments of the present disclosure aredescribed with reference to the accompanying Drawings. Each of theexemplary embodiments described below shows a desirable specificexample. The structural elements, the arrangement and connection of thestructural elements, steps, the processing order of the steps etc. shownin the following exemplary embodiments are mere examples, and thereforedo not limit the present disclosure. Therefore, among the structuralelements in the following embodiments, structural elements not recitedin any one of the independent claims defining the most generic part ofthe present disclosure are described as arbitrary structural elements.

Embodiment 1

Referring to FIG. 1 to FIG. 6B, descriptions are given of an imagecoding method, and an image coding apparatus which executes the imagecoding method according to Embodiment 1.

The image coding apparatus has a function to generate, for each PU, modeinformation indicating the intra prediction mode used for intraprediction. In Embodiment 1, an example case is described where thenumber of candidate intra prediction modes is fixed to two in advance(the fixed number that is two or more candidate intra prediction modesare constantly derived). It is to be noted that the same methods mayalso be used in a case where the number of candidate intra predictionmodes is fixed to three or more or a case where the number of candidateintra prediction modes is set to be a variable value that is two ormore.

[1-1. Configuration of Image Coding Apparatus]

Referring to FIG. 1, a description is given of a configuration of animage coding apparatus according to Embodiment 1. FIG. 1 is a blockdiagram illustrating a configuration of an image coding apparatus 100.

The image coding apparatus 100 receives an input of an image signal,codes the image signal, and outputs, to an image decoding apparatus (notshown in FIG. 1), a bitstream (bitStr) that is output from a variablelength coding unit 120 to be described later.

As shown in FIG. 1, the image coding apparatus 100, for example,includes: a subtraction unit 101 which outputs a subtracted imagebetween an image indicated by an image signal and a prediction image; atransform unit 102 which performs, for example, discrete cosinetransform (DCT) on the subtracted image; a quantization unit 103 whichquantizes the subtracted image which underwent DCT; an inversequantization unit 104 which performs inverse quantization; an inversetransform unit 105 which performs, for example, inverse DCT; an additionunit 106 which adds a previous prediction image and a subtracted imagereconstructed by the inverse transform unit 105 to output a previousimage; an inter prediction unit 107 which generates a prediction imageby inter frame prediction; an intra prediction unit 108 which generatesa prediction image by intra prediction; a switching unit 109 whichselectively outputs the prediction image from the inter prediction unit107 and the prediction image from the intra prediction unit 108; acoding control unit 100 which controls each function of the image codingapparatus 100; and a variable length coding unit 120 which performsvariable length coding on the data from the quantization unit 103.

The coding control unit 110 holds a “target mode number” and a “variablelength coding method” that should be applied to a coding target block(PU or a block included in the PU, and this is applied hereinafter)determined according to a predetermined evaluation standard. Theevaluation standard is set, for example, so as to reduce the number ofbits of code strings that are output under a condition for achieving apredetermined prediction accuracy.

According to the “target mode number” specified by the coding controlunit 110, the intra prediction unit 108 predicts the pixel value of acurrent coding target block by utilizing a prediction pixel located in adirection specified by the intra prediction mode indicated by the targetmode number. In addition, the intra prediction unit 108 codes the“target mode number” to generate the “coding mode number”.

The variable length coding unit 120 performs entropy coding such asarithmetic coding of the “coding mode number” generated by the intraprediction unit 108, according to the “variable length coding method”specified by the coding control unit 110 so as to output a bit stream(bitStr).

[1-2. Procedure of Image Coding Method]

Referring to FIG. 2, a description is given of an image coding methodaccording Embodiment 1. FIG. 2 is a flowchart of a mode informationgenerating method executed by the image coding apparatus shown in FIG.1.

The coding control unit 110 first obtains the “target mode number” ofthe coding target block for which mode information is generated (StepS201).

The coding control unit 110 then obtains candidate intra predictionmodes for the coding target block to obtain a “prediction mode array”(candModeList) (Step S203). In Embodiment 1, the number of candidateintra prediction modes is fixed to two; and thus, the number of elementsincluded in the prediction mode array is two. When the number ofcandidate intra prediction modes is fixed to three or more, the numberof elements included in the prediction mode array equals the number ofcandidate intra prediction modes. When the number of candidate intraprediction modes is set to be variable, the number of elements in theprediction mode array equals the maximum number of candidate intraprediction modes.

The prediction mode array is an array in which each element has an indexvalue (starting with 0) which is the “candidate prediction mode number”to be described later. The details of the method of obtaining thecandidate intra prediction modes in this step will be described laterwith reference to FIG. 4.

Next, whether or not the target mode number matches the value of any oneof the elements of the prediction mode array is determined (Step S205).

(Case where Target Mode Number Matches Value of any One of Elements ofPrediction Mode Array)

When the determination in Step S205 shows that “the target mode numbermatches the value of any one of the elements of the prediction modearray” (YES in Step S205), the coding control unit 110 determines thevalue of the prediction mode use flag to be “1” (Step S207).

The coding control unit 110 performs variable length coding (Step S209)on the candidate prediction mode numbers (index values of the predictionmode array) according to a specified scheme, in order to identify theprediction mode used among the candidate intra prediction modes obtainedin Step S203.

(Case where Target Mode Number does not Match Value of any One ofElements of Prediction Mode Array)

When the determination in Step S205 shows that “the target mode numberdoes not match the value of any one of the elements of the predictionmode array” (NO in Step S205), the coding control unit 110 determinesthe “prediction mode use flag” to be 0 (Step S213).

The coding control unit 110 then generates, based on the target modenumber and the number of candidate intra prediction modes, a “codingmode number” (the value of rem_intra_luma_pred_mode”) (Step S215). Inthis step, different coding mode numbers are generated based on thetarget mode number and according to the number of candidate intraprediction modes, even in the case of the same target mode number. Thestep (S215) will be described later with reference to FIG. 3.

Lastly, the coding control unit 110 codes the coding mode numberaccording the specified variable length coding method (Step S217). Thestep (S217) will be described later with reference to FIG. 5 (CABACscheme) and FIG. 8 (CAVLC scheme).

[1-2-1. Example of Generation of Coding Mode Number]

A description is given of an example of Step S215 for generating thecoding mode number. FIG. 3 is a flowchart of an example of Step S215 forgenerating the coding mode number. The coding mode number may begenerated by other methods.

First, the coding control unit 110 obtains the total number of intraprediction modes (the number of types of the intra prediction modes,which is 34 in Embodiment 1) and the number of candidate intraprediction modes (Step S301). In Embodiment 1, as described earlier, thenumber of candidate intra prediction modes is a fixed number that istwo.

The coding control unit 110 repeats the loop specified as Step S302 toStep S307 by the number of times specified by the number of candidateintra prediction modes. In Embodiment 1, the number of candidate intraprediction modes is 2; and thus, Step S303 (and Step S305 depending onthe determination in Step S303) is executed twice when the values of theindices (i) are 1 and 0. When the number of candidate prediction modesis N, Step S303 (and Step S305 depending on the determination in StepS303) is executed N times.

In Step S302, i is set to 0.

In Step S303, a determination is made on whether or not the value of thetarget mode number at a current time point is larger than the value ofthe element specified by the index (i) in the prediction mode array.When the determination shows that the value of the target mode number atthe current time point is larger than the value of the specifiedelement, the value of the target mode number at the current time pointis decremented by 1 (Step S305).

This is repeated by the number of times specified by the value of thenumber of candidate intra prediction modes, and the current target modenumber reflecting the result of the decrement or the like in Step S305is finally determined to be the “coding mode number” (Step S309).

The processing of Step S215 is equivalent to, for example, determining,in association with the “coding mode number”, the value of the “targetmode number” which takes any one of the total thirty-four values from 0to 33.

Table 1 shows the associations between (a) target mode numbers and (b)“coding mode numbers” in the case where the “number of candidateprediction modes” is two (where there are indices 0 and 1). In Table 1,(c) indicates process of Step S305 (a changed value from the currenttarget mode number) when i=0, and (d) indicates that process of StepS305 (a changed value from the current target mode number) when i=1. InTable 1, candModeList[0] indicates the first element in the predictionmode array, and candModeList[1] indicates the second element in theprediction mode array.

TABLE 1 (a) Target 0 1 2 . . . CandModeList . . . CandModeList . . . 33mode [0] [1] number 0 . . . 33 (c) S305 0 0 0 0 Yes −1 −1 −1 −1 (i = 0)(S205) (d) S305 0 0 0 0 0  0 Yes −1 −1 (i = 1) (S205) (b) 0 1 2 . . .Unnecessary . . . Unnecessary . . . 31 Coding (S205) (S205) mode number(0 . . . 31)

From Table 1, the coding mode number can be derived as described belowaccording to the value of the target mode number.

(1) The target mode number matches the coding mode number when 0≤targetmode number<the value of the first element of the prediction mode array(0≤target mode number<candModeList[0]) is satisfied.

(2) The coding mode number is a number smaller than the target modenumber by 1 when the value of the first element of the prediction modearray<target mode number<the value of the second element of theprediction mode array (candModeList[0]<target modenumber<candModeList[1]) is satisfied.

(3) The coding mode number is a number smaller than the target modenumber by 2 when the value of the second element of the prediction modearray<target mode number (candModeList[1]<target mode number) issatisfied.

In other words, when the prediction mode array is composed of k numberof elements (when there are k number of candidate intra predictionmodes), it is possible to sort the elements based on the values in theprediction mode array, compare the target mode number with each of theelements arranged in the prediction mode array to determine the positionof the element at which the target mode number is larger than the valuein the prediction mode array.

(k) The coding mode number is smaller than the target mode number by k−1when the value of the (k−1)th element of the prediction modearray<target mode number<the value of the kth element (whencandModeList[K−1]<target mode number<candModeList[k]) is satisfied.[1-2-2. Method of Generating Prediction Mode Array]

Referring to FIG. 4, a description is given of a method of determining a“prediction mode array” (candModeList). FIG. 4 is a flowchart of adetail of the prediction mode array obtaining step (Step S203) shown inFIG. 2. Here, a description is given of the case where the “predictionmode array” (candModeList) of the coding target block is determined whenthe number of the candidate intra prediction modes is fixed to two.

In Embodiment 1, the target mode numbers of adjacent blocks that havealready been coded are used as the elements of the “prediction modearray” (candModeList). In the case where the number of target modenumbers of adjacent blocks that have already been coded is less than thenumber of elements of the prediction mode array as in the case where thetarget mode numbers of adjacent blocks match one another (the matchedtarget mode number is assumed to be one candidate intra predictionmode), candidate intra prediction modes are determined from intraprediction modes other than the target mode numbers of adjacent blocks,such as DC prediction mode, plane prediction (intra planar), andvertical prediction (intra angular).

The coding control unit 110 sets the target mode number of the alreadycoded block to the left of the coding target block to intraPredModeLeft(Step S401).

More specifically, for example, when the left adjacent block is codedusing intra prediction, the target mode number used in the coding(decoding) is set to intraPredModeLeft. When the left adjacent block iscoded using a coding method other than intra prediction (for example,inter frame coding), the intra prediction mode number (for example, “2”)indicating DC prediction mode (indicated as DC prediction in FIG. 4) isset to intraPredModeLeft. When it is determined that the left adjacentblock does not exist (for example, in the case of slice boundary orpicture edge), Not Available is set to intraPredModeLeft.

In the similar manner, the coding control unit 110 sets the target modenumber of the already coded block above the coding target block tointraPredModeAbove (Step S402). The method for settingintraPredModeAbove is the same as the processing performed on the leftadjacent block (Step S401) other than the position of the block.

After setting intraPredModeLeft and intraPredModeAbove, the codingcontrol unit 110 determines if the target mode numbers of the left andabove adjacent blocks are non-existent (if both of intraPredModeLeft andintraPredModeAbove indicate Not Available) (Step S403).

Here, in the case of YES in Step S403 (where both of the left and aboveadjacent blocks are non-existent), the coding control unit 110 sets anintra prediction mode number “0” to list 0 (candModeList[0]) that is thefirst element of the “prediction mode array” (candModeList) of thecoding target block and sets an intra prediction mode number indicatingDC prediction mode (for example, “2”) is set to list 1 (candModeList[1])that is the second element of the “prediction mode array” (Step S404).

In the case of NO in Step S403, the coding control unit 110 determinesif one of intraPredModeLeft and intraPredModeAbove is non-existent, orwhether or not intraPredModeLeft and intraPredModeAbove match oneanother (Step S405).

In the case of No in Step S405 (when the target mode numbers of both ofthe left and above adjacent blocks exist but they do not match oneanother), the coding control unit 110 sets, to list 0 (candModeList[0])of the “prediction mode array” (candModeList) of the coding targetblock, the target mode number which is the smaller of the target modenumber of the left adjacent block and the target mode number of theabove adjacent block. The coding control unit 110 further sets, to list1 (candModeList[1]), the target mode number which is the larger of thetarget mode number of the left adjacent block and the target mode numberof the above adjacent block (Step S406).

In the case of YES in Step S405 (where only one of the target modenumbers of the left and above adjacent blocks exists, or where thetarget mode numbers of the left and above adjacent blocks match oneanother), the coding control unit 110 determines whether the matchedtarget mode number or the target mode number which exists (hereinafter,referred to as “adjacent mode number”) is an intra prediction modenumber (for example, “2”) which indicates DC prediction mode (StepS407).

In the case of Yes in Step S407 (where the adjacent mode number is anintra prediction mode number which indicates DC prediction mode), thecoding control unit 110 sets, to list 0 (candModeList[0]) in the“prediction mode array” (candModeList) of the coding target block, theintra prediction mode number which is the smaller of the adjacent modenumber (the matched target mode number or the target mode number whichexists) and the intra prediction mode number which indicates DCprediction mode. The coding control unit 110 further sets, to list 1(candModeList[1]), the intra prediction mode number which is the largerof the adjacent mode number (the matched target mode number or thetarget mode number which exists) and the intra prediction mode numberwhich indicates DC prediction mode (Step S408).

In the case of NO in Step S407 (where the adjacent mode number is notthe intra prediction mode number (for example, “2”) which indicates DCprediction mode), the coding control unit 110 determines whether or notthe adjacent mode number is “0” (Step S409).

In the case of NO in Step S409 (where the adjacent mode number is not“0”), the coding control unit 110 sets an intra prediction mode number“0” to list 0 (candModeList[0]), and sets the adjacent mode number tolist 1 (candModeList[1]), in the “prediction mode array” (candModeList)of the coding target block (Step S410).

In case of YES in Step S409 (where the adjacent mode number is “0”), thecoding control unit 110 sets the adjacent mode number “0” to list 0(candModeList[0]), and sets an intra prediction mode number “1” to list1 (candModeList[1]), in the “prediction mode array” (candModeList) ofthe coding target block (Step S411).

In Steps S408 to S411, the DC prediction mode number and the intraprediction mode numbers “0” and “1” are preferentially assigned to eachelement of the prediction mode array. As a result, as shown in Table 1above, the coding mode numbers can be made smaller, leading to anincrease in the coding efficiency.

The preferential order here (DC prediction mode number, intra predictionmode numbers “0” and “1”) is merely an example. By prioritizing thesmaller intra prediction mode number, it is possible to increase thecoding efficiency even when the priority of the DC prediction mode islowered.

[1-2-3. Coding of Coding Mode Number]

Referring to FIG. 5, a description is given of an example of Step S217for coding the coding mode number. The coding in the example isperformed according to a specified variable length coding and the CABACscheme. FIG. 5 is a flowchart of a coding method according to the CABACscheme.

The coding control unit 110 obtains a coding mode number, for example,according to the method shown in FIG. 3 (Step S701 and Step S215), andperforms binarizing process on the obtained coding mode number accordingto a binarizing method corresponding to the total number of intraprediction modes (the maximum number of modes) (Step S702). This meansthat, for example, in the case where the maximum number of modes variesdepending on the coding unit of the intra prediction mode (for example,17 modes when the coding unit is size 4×4, and 34 modes when the codingunit is size 8×8 or larger), binarizing processing is performedcorresponding to the size.

The coding control unit 110 performs binary arithmetic coding on thesignal in which the coding mode number is binarized (Step S703). Thisallows the coding mode number to be recorded on the stream.

Referring to FIG. 6A and FIG. 6B, descriptions are given of syntaxexamples showing specific data structure. FIG. 6A is a conceptualdiagram illustrating an example of a syntax structure, extracted fromNPL 1, which indicates a data structure storing target mode numbers.FIG. 6B is a conceptual diagram illustrating an example of a syntaxstructure according to Embodiment 1.

Portions not particularly mentioned here are assumed to operate asmentioned in NPL 1. In the conventional syntax structure, a predictionmode use flag (prev_intra_luma_pred_flag) is first coded.

When the prediction mode use flag indicates 1, it is determined whetherthe number of candidate intra prediction modes (NumMPMCand) is largerthan one (901). When the number of candidate intra prediction modes(NumMPMCand) is larger than one (two or more), the candidate predictionmode number (mpm_idx) is coded.

When the prediction mode use flag indicates 0, the coding mode number(rem_intra_luma_pred_mode) is coded.

In the configuration according to the present disclosure, the number ofcandidate intra prediction modes is fixed to at least two or more; andthus, the conditional expression 901 “if(NumMPMCand>1)” in FIG. 6A isunnecessary, resulting in the bit stream having the syntax structureshown in FIG. 6B. In other words, when the prediction mode use flag is1, the candidate prediction mode number (mpm_idx) is always coded. Thisresults in less conditional branching, allowing the generation of abitstream which can be decoded with reduced processing amount. Althoughnot shown in the drawings, conventionally, after Step S207 in FIG. 2,process is performed for determining whether or not the target modenumber of the left adjacent block matches the target mode number of theabove adjacent block. When the target mode numbers match one another,Step S209 is performed.

Variation of Embodiment 1

(Variation 1: Variation of Prediction Mode Determining Method)

The method of determining the prediction mode array described withreference to FIG. 4 may be varied as follows.

In Variation 1, aside from the target mode numbers used for the adjacentblocks, an intra prediction mode number which has the highestprobability of occurrence for a coding target block is selected as amost frequent mode number. Then, the most frequent mode number isreplaced with one of the “DC prediction mode 2”, “mode number 0” and“mode number 1” shown in FIG. 4.

For selecting the most frequent mode number, for example, the intraprediction mode number having the minimum code length may be selectedaccording to the context state used in the arithmetic coding in StepS703 of FIG. 5. Furthermore, for example, the intra prediction modenumber assigned to the minimum bit length according to the variablelength table used in Steps S502 and S503 of FIG. 8 that will bedescribed later, may be determined as the most frequent mode number. Itmay also be that the most frequent mode number is selected according toa totally different method (for example, statistically deriving the mostfrequent mode number from histories of adjacent mode numbers andcumulative target mode numbers). The first two methods can increase thecoding efficiency without increasing the processing amount by sharingthe existing steps. The last method is expected to significantlyincrease the coding efficiency although the processing amount slightlyincreases.

Referring to FIG. 7, a description is given of a method of determining aprediction mode array using the most frequent mode number. FIG. 7 is aflowchart of an example of the step for determining the prediction modearray (Step S203). The procedure shown in the flowchart of FIG. 7 is avariation of the procedure shown in the flowchart of FIG. 4. The Steps(Steps S401 to S403 and S405 to S408) in FIG. 7 are the same as those inFIG. 4, other than Step S404 (Step S804) Step S409 (Step S809), StepS410 (Step S810), and Step S411 (Step S811). Thus, descriptions of theduplicated steps may be omitted appropriately.

Here, a description is given of the case where the “prediction modearray” (candModeList) of the coding target block is determined when thenumber of the candidate intra prediction modes is fixed to two.

The coding control unit 110 sets, to intraPredModeLeft, the target modenumber of the already coded block to the left of the coding target block(Step S401), and set, to intraPredModeAbove, the target mode number ofthe already coded block above the coding target block (Step S402).

After setting intraPredModeLeft and intraPredModeAbove, the codingcontrol unit 110 determines if the target mode numbers of the left andabove adjacent blocks are non-existent (if both of intraPredModeLeft andintraPredModeAbove indicate Not Available) (Step S403).

In the case of YES in Step S403 (where both of the left and aboveadjacent blocks are non-existent), the coding control unit 110 sets, tolist 0 (candModeList[0]) in the “prediction mode array” of the codingtarget block, the intra prediction mode number which is the smaller ofthe most frequent mode number and the intra prediction mode numberindicating DC prediction mode (for example, “2”). The coding controlunit 110 further sets, to list 1 (candModeList[1]), the intra predictionmode number which is the larger of the most frequent mode number and theintra prediction mode number indicating DC prediction mode (for example,“2”) (Step S804).

In the case of NO in Step S403, the coding control unit 110 determinesif one of intraPredModeLeft and intraPredModeAbove is non-existent, orwhether or not intraPredModeLeft and intraPredModeAbove match oneanother (Step S405).

In the case of NO in Step S405 (where the target mode numbers of both ofthe left and above adjacent blocks exist but they do not match oneanother), the coding control unit 110 sets, to list 0 (candModeList[0])of the “prediction mode array” (candModeList) of the coding targetblock, the target mode number which is the smaller of the target modenumber of the left adjacent block and the target mode number of theabove adjacent block. The coding control unit 110 further sets, to list1 (candModeList[1]), the target mode number which is the larger of thetarget mode number of the left adjacent block and the target mode numberof the above adjacent block (Step S406).

In the case of YES in Step S405 (where only one of the target modenumbers of the left and above adjacent blocks exists, or where thetarget mode numbers of the left and above adjacent blocks match oneanother), the coding control unit 110 determines whether the matchedtarget mode number or the target mode number which exists (adjacent modenumber) is an intra prediction mode number (for example, “2”) whichindicates DC prediction mode (Step S407).

In the case of Yes in S407 (where the adjacent mode number is an intraprediction mode number which indicates DC prediction mode), the codingcontrol unit 110 sets, to list 0 (candModeList[0]) in the “predictionmode array” (candModeList) of the coding target block, the intraprediction mode number which is the smaller of the adjacent mode number(the matched target mode number or the target mode number which exists)and the intra prediction mode number which indicates DC prediction mode.The coding control unit 110 further sets, to list 1 (candModeList[1]),the intra prediction mode number which is the larger of the adjacentmode number (the matched target mode number or the target mode numberwhich exists) and the intra prediction mode number which indicates DCprediction mode (Step S408).

In the case of NO in Step S407 (where the adjacent mode number is notthe intra prediction mode number (for example, “2”) which indicates DCprediction mode), the coding control unit 110 determines whether or notthe adjacent mode number is the most frequent mode number (Step S809).

In the case of NO in Step S809 (where the adjacent mode number is notthe most frequent mode number), the coding control unit 110 sets, tolist 0 (candModeList[0]), the intra prediction mode number which is thesmaller of the most frequent mode number and the adjacent mode number,and sets, to list 1 (candModeList[1]), the intra prediction mode numberwhich is the larger of the most frequent mode number and the adjacentmode number, in the “prediction mode array” of the coding target block(Step S810).

In the case of YES in Step S809 (where the adjacent mode number is themost frequent mode number), the coding control unit 110 sets, to list 0(candModeList[0]), the intra prediction mode number which is the smallerof the adjacent mode number (=most frequent mode number) and the intraprediction mode number indicating DC prediction mode, and sets, to list1 (candModeList[1]), the intra prediction mode number which is thelarger of the adjacent mode number (=most frequent mode number) and theintra prediction mode number indicating DC prediction mode, in the“prediction mode array” of the coding target block (Step S811).

In Steps S809 to S811, as described above, the most frequent mode numberand the DC prediction mode number are preferentially assigned torespective elements of the prediction mode array. As a result, it ispossible to increase matching ratio to the intra prediction mode. Inaddition, as shown in Table 1, coding mode numbers can be made smaller,leading to an increase in the coding efficiency.

The preferential order here (the preferential order of DC predictionmode number, most frequent mode number, and intra prediction mode number“0”) is merely an example, and may be changed based on the statisticalinformation. The intra prediction mode number “0” indicates, forexample, plane prediction (intra planar) and vertical prediction (intraangular).

(Variation 2: Variation of Coding of Coding Mode Number)

Coding of the coding mode numbers may be performed according to not onlythe CABAC scheme, but also a CAVLC scheme. Hereinafter, the codingmethod according to the CAVLC scheme will be described with reference toFIG. 8, FIG. 9A and FIG. 9B. FIG. 8 is a flowchart of a coding methodaccording to the CAVLC scheme. FIG. 9A is an example of a coding tablewhen the maximum number of modes (total number of intra predictionmodes) is 17. FIG. 9B is an example of a coding table when the maximumnumber of modes is 34.

The coding control unit 110 obtains a coding mode number (Step S501),for example, according to the method shown in FIG. 3, and selects avariable length table (not shown) corresponding to the maximum number ofmodes (Step S502). This means that in the case where, for example, themaximum number of modes varies depending on the size of the coding unit(for example, 17 modes for the coding unit size of 4×4 and 34 modes forthe coding unit size of 8×8 or larger), the variable length table whichcorresponds to the coding unit size is selected.

According to Embodiment 1, it is sufficient that one kind of variablelength table is used for each coding unit; and thus, the memory amountnecessary for a coding apparatus can be reduced.

The coding control unit 110 derives a coding index number from thecoding mode number using the selected variable length table (Step S503).The variable length table is updated per block, large block or slicebasis such that the coding index decreases as the frequency of thecoding mode number increases. Thus, the variable length coding process,which will be described later, is performed such that the code lengthdecreases as the coding index number decreases.

Lastly, the coding control unit 110 codes the derived coding indexnumber using a predetermined coding table (Step S504).

In the process in FIG. 2, setting of the prediction mode use flag (StepS207) and coding of the coding mode number (Step 209) are performedseparately. However, an example is given here of a case where the codingmode number is coded including the prediction mode flag in the CAVLCscheme.

In FIG. 9A and FIG. 9B, MPM1 indicates the case where the predictionmode use flag=1 and the candidate prediction mode number is 0. In thiscase, MPM1 has a code “10”. MPM2 indicates the case where the predictionmode use flag=1 and the candidate prediction mode number is 0. In thiscase, MPM 2 has a code “11”. The following left numbers 0 to 14(corresponding to 15 modes obtained by subtracting 2 modes from 17 modesas this is the example where the number of candidate intra predictionmodes is two), and 0 to 31 (corresponding to 32 modes obtained bysubtracting 2 modes from 34 modes as this is the example where thenumber of candidate intra prediction modes is two) indicate the codingmode numbers derived in (Step S503). The right codes indicate codestrings written to bit streams.

This method allows all mode information to be coded in the samemechanism, reducing the necessary memory amount.

In the same manner as the flow shown in FIG. 2, the prediction mode useflag and the coding mode number may be separately coded. In this case,with the code for MPM1 being 1 and the prediction mode use flag=1, 1 bitindex may be coded for the prediction mode number.

For the coding according to the CAVCL scheme, a vlc table may bereferred to which is shared between the prediction mode use flag(prev_intra_luma_pred_flag), the candidate prediction mode number(mpm_idx), and the coding mode number (rem_intra_luma_pred_mode).

Embodiment 2

Referring to FIG. 10 to FIG. 15, descriptions are given of an imagedecoding method and an image decoding apparatus which executes the imagedecoding method according to Embodiment 2.

In the image decoding method according to Embodiment 2, arithmeticdecoding is performed using only the result of the arithmetic decodingperformed on the bit stream of a decoding target block. In arithmeticdecoding process, information amount of 1 bit to a few bits may bereconstructed, making it difficult to secure buffer amount and toperform real-time processing. However, the image decoding methodaccording to Embodiment 2 does not use information of other decodingtarget blocks, resulting in reducing internal memory amount necessaryfor calculation and reducing processing time.

[2-1. Configuration of Image Decoding Apparatus]

Referring to FIG. 10, a description is given of a configuration of theimage decoding apparatus according to Embodiment 2. FIG. 10 is a blockdiagram illustrating a configuration of an image decoding apparatus 200.

The image decoding apparatus 200 is an apparatus which receives an inputof a bit stream (bitStr), and outputs an image signal. In the presentdisclosure, an example is given of a case where a bit stream (bitStr) tobe input is generated by the image coding method according toEmbodiment 1. For the bit stream to which a code string shown in FIG. 9Aor FIG. 9B is written, following the definition of Prediction UnitSyntax from left to right in FIG. 9A or FIG. 9B in a sense of datastructure, variable length decoding (Step S1117) of the right part isperformed, a “coding mode number” (rem_intra_luma_pred_mode) is obtained(Step S1115), and a “target mode number” is obtained.

The image decoding apparatus 200 includes: a variable length decodingunit 220, an inverse quantization unit 201, an inverse transform unit202, an addition unit which adds a previous prediction image and asubtracted image, an inter prediction unit 204 which generates aprediction image by inter frame prediction, an intra prediction unit 205which generates a prediction image by intra prediction, a switching unit206 which selectively outputs the prediction image from the interprediction unit 204 and the prediction image from the intra predictionunit 205, a control unit 210, and so on.

The variable length decoding unit 220 performs operations inverse tooperations by the variable length coding unit 120. In other words, thevariable length decoding unit 220 receives an input of the bit stream,and obtains a “coding mode number” etc. from the bit stream according tothe number of candidates for the intra prediction mode (NumMPMCand).Furthermore, the variable length decoding unit 220 obtains a “targetmode number” from the “coding mode number”.

The intra prediction unit 205 performs approximately the same operationsas operations by the intra prediction unit 108 in FIG. 1. According tothe obtained “target mode number”, the intra prediction unit 205predicts the pixel value of a current decoding target block by utilizinga prediction pixel located in a direction specified by an intraprediction mode corresponding to the target mode number.

The control unit 210 provides information necessary for obtaining thetarget mode number to the variable length decoding unit 220. Thenecessary information in the decoding method according to the presentdisclosure may be any information for reproducing the “target modenumber” from the bit stream output as a result of the coding accordingto Embodiment 1. For example, when the variable length decoding unit 220does not hold such information, a prediction mode array (candModeList)about the decoding target block (or an initial value of this list) isprovided thereto. In addition, an entropy decoding mode (for example, abit string output according to the CAVLC scheme or a bit string outputaccording to the CABAC scheme) is provided for each predetermined unitassociated with the current decoding target block.

[2-2. Procedure of Image Decoding Method]

Referring to FIG. 11, a description is given of the image decodingmethod according Embodiment 2. FIG. 11 is a flowchart of a method ofdecoding a “target mode number” (34 intra prediction modes shown in FIG.15) executed by the image decoding apparatus in FIG. 10. In Embodiment2, a description is given of an example where each step is executed bythe variable length decoding unit 220; however, each step may beexecuted by, for example, the control unit 210.

First, the variable length decoding unit 220 extracts a portioncorresponding to mode information of a decoding target block from thebit stream (bitStr) coded by the coding method according toEmbodiment 1. The corresponding portion is a bit string obtained byperforming entropy coding on one of (1) a “prediction mode use flag”(prev_intra_luma_pred_flag), (2) a “candidate prediction mode number”(mpm_idx), and (3) a “coding mode number” (rem_intra_lyma_pred_mode)which are structured according to a syntax (Prediction unit syntax)explained with reference to FIGS. 6A and 6B.

After obtaining the bit string, the variable length decoding unit 220decodes the bit string according to the syntax in FIG. 6A or FIG. 6B toobtain the “target mode number” (Step S1103 to Step S1115).

The variable length decoding unit 220 first reconstructs the value ofthe “prediction mode use flag” (prev_intra_luma_pred_flag) according toa predetermined entropy decoding method (Step S1103). Hereinafter,unless specifically explained, the following descriptions, the words inthe diagrams, and the values have the same meaning as those in thecoding method according to Embodiment 1 and the descriptions about thesyntax in FIGS. 6A and 6B.

The variable length decoding unit 220 determines whether or not thedecoded prediction mode use flag indicates 1 (Step S1105).

In the case of YES in Step S1105 (where the value of the “predictionmode use flag” indicates 1), the variable length decoding unit 220decodes the “candidate prediction mode number” (mpm_idx) (Step S1109).

More specifically, the variable length decoding unit 220 generates aprediction mode array (candModeList), and determines, as the “targetmode number”, the value (candModeList [mpm_idx] of the element havingthe element number (mpm_idx) in the prediction mode array (candModeList)(Step S1111). For generating the prediction mode array, the methoddescribed with reference to FIG. 4 or FIG. 7 according to Embodiment 1may be used. It is assumed that the same prediction mode arraygenerating method is used between the coding apparatus and the decodingapparatus.

In the case of NO in Step S1105 (where the value of the “prediction modeuse flag” is not 1), the variable length decoding unit 220 performsentropy decoding on the coding mode number. More specifically, thevariable length decoding unit 220 first obtains the coding mode numberfrom the bit string according to the total number of intra predictionmodes (the maximum number of modes) (Step S1117). This obtainmentprocess is inverse to the process in Step S217 in FIG. 2. Differentprocesses are performed depending on whether the corresponding bitstring is output according to a (1) CABAC scheme (FIG. 5) or a (2) CAVLCscheme (FIG. 8) as the entropy coding scheme. The entropy coding schemeis determined, for example, based on the value indicated by an entropycoding mode flag of a predetermined unit corresponding to a predictionunit (PU) associated with a decoding target block. The flag may beidentified in a higher sequence unit.

First, a description is given of a case where the bit string is outputaccording to the (1) CABAC scheme, with reference to FIG. 12A. FIG. 12Ais a flowchart of arithmetic decoding process corresponding to StepS1117 in FIG. 11.

The variable length decoding unit 220 first performs arithmetic decodingon the obtained bit stream (Step S1401, inverse to Step S703). Thevariable length decoding unit 220 performs value multiplexing process onthe binary information obtained by the arithmetic decoding toreconstruct to the coding mode number (Step S1402).

Next, a description is given of a case where the bit string is outputaccording to the (2) CAVLC scheme, with reference to FIG. 13. FIG. 13 isa flowchart of a method of obtaining the “coding mode number” in StepS1117 when the bit string is output according to the CAVLC scheme.

The variable length decoding unit 220 first obtains a coding indexnumber from the bit string using information (context) necessary fordecoding the “coding mode number” of the decoding target block (PU)(Step S1201). The decoding process corresponds to the process inverse tothe coding process in Step S504 in FIG. 8. More specifically, a variablelength coding (variable length decoding) table shown in FIG. 9A or FIG.9B is selected according to the maximum number of modes (for example, 17modes or 34 modes depending on the transmission unit of the predictioninformation described in Embodiment 1). From bit strings in the selectedvariable length coding table, the bit string corresponding to the inputbit stream (bit string shown at the right side in FIG. 9A or FIG. 9B) issearched for, and the coding index number (corresponds to the numbershown at the left side in FIG. 9A or FIG. 9B) associated with the bitstring is obtained.

The variable length decoding unit 220 then selects different variablelength tables for each maximum number of modes in the similar manner asdescribed above (Step S1202 which is the same as Step S502, not shown),and derives the coding mode number associated with the obtained codingindex number, using the selected variable length table (S1203 which isthe processing inverse to Step S503). The variable length table isupdated per block, large block, or slice basis such that the codingindex number decreases as the frequency of the coding mode numberincreases. The update is performed according to a method predeterminedbetween the coding apparatus and the decoding apparatus; and thus, it isdesigned such that the same variable length table is used for coding acoding target block and decoding a decoding target block. The codingmode number is reconstructed according to this processing.

Next, the target mode number is reconstructed from the coding modenumber (Step S1115 which is the process inverse to Step S215 in FIG. 2).FIG. 14 is a flowchart of process for reconstructing the target modenumber from the coding mode number.

As shown in FIG. 14, the variable length decoding unit 220 obtains the“target mode number” from the “coding mode number” obtained in StepS1117. The respective steps in FIG. 14 are executed as the steps inverseto the steps of obtaining the “coding mode number” from the “target modenumber” of FIG. 3.

The variable length decoding unit 220 first obtains the number ofcandidate intra prediction modes (NumMPMCand) (Step S1301). InEmbodiment 2, the number of candidate intra prediction modes is also twothat is a fixed number as in Embodiment 1.

The variable length decoding unit 220 then repeats the loop specified asStep S1302 to Step S1307 by the number of times specified by the numberof candidate intra prediction modes (NumMPMCand). In Embodiment 2, thenumber of candidate intra prediction modes (NumMPMCand) is two; andthus, Step S1303 (and Step S1305) is (are) executed twice in total whenthe values of the indices are 0 and 1. When the number of candidateprediction modes is N, Step S1303 (and Step S1305 depending on thedetermination in Step S1303) is executed N times.

In Step S1302, the candidate index candIdx (corresponds to Index in FIG.14) is set to 0.

In Step S1303, the current coding mode number is compared with the valueof the element specified by the value of a candidate index candIdx inthe prediction mode array (CandModeList) (the value of candModeList[candIdx]). When Index=0, the coding mode number is the coding modenumber at the time of obtainment in Step S1117.

In the case of YES in Step S1303 (where the coding mode number≥the valueof candModeList[candIdx] is satisfied, the coding mode number isincremented by 1 (Step S1305). Here, the coding mode number isincremented by 1 also in the case where the current coding mode numberis the same as the value of the prediction mode array,candModeList[candIdx]. The loop from S1302 to S1307 is repeated whileincrementing the candidate index number candIdx by 1 until thecomparison about all the candidate indices is completed.

Through this processing, the coding mode number is reconstructed intothe target mode number according to the number of candidate intraprediction modes. Here, reconstructing the “target mode number” from the“coding mode number” according to the number of candidate intraprediction modes is equivalent to performing the process in Table 1 fromthe lowermost line to the uppermost line.

For example, when the number of candidate intra prediction modes (thevalue of NumMPMCand) is 2, the associations between coding mode numbersand target mode numbers are as shown in Table 2. This table is forexplaining an exemplary case where the value of the first element(having an index 0) of the prediction mode array is assumed to be “i”,and the value of the second element (having an index 1) of theprediction mode array is assumed to be “j”.

TABLE 2 (d) Coding 0 1 . . . i . . . j . . . 30 31 mode (candModeList(candModeList number [0]) [1]) (0 . . . 31) S1105 0 0 0 +1 +1 +1 +1 +1+1 S1105 0 0 0 0  0 +1 +1 +1 +1 (a) 0 1 . . . Unnecessary . . .Unnecessary . . . 32 33 Decoding (candModeList (candModeList mode [0])[1]) number (0 . . . 33)

In this way, the decoding apparatus and decoding method according toEmbodiment 2 switch, according to the numbers of candidate intraprediction modes (or based on the number of candidate intra predictionmodes), the associations between CodeNum and the “coding mode numbers”in the CAVLD scheme and the associations with the “coding mode numbers”from the binary arrays in the CABAC scheme (Step S1117). Furthermore,the associations between coding mode numbers and target mode numbers areswitched according to the number of candidate intra prediction modes(S1115).

With the configuration, it is possible to reconstruct the original“target mode number” from the bit stream according to Embodiment 1generated by switching the schemes for coding the target mode numberaccording to the number of candidate intra prediction modes, with anincreased coding efficiency.

As described earlier, in the image decoding apparatus and the imagedecoding method according to the present disclosure, the number ofcandidate intra prediction modes is fixed to two or more; and thus, itis possible to perform arithmetic decoding without requiring conditionalbranching for determining whether or not the number of candidate intraprediction modes is one.

FIG. 12B is a conceptual diagram for illustrating an example of the flowof the arithmetic decoding process performed in the image decodingapparatus. As described earlier, the information amount of the decodedsignal (decoding parameter) for the bit length to be obtained isdetermined at an arithmetic rate in the arithmetic decoding; and thus,the information amount is indeterminate. In order for real-timeprocessing, high-speed calculations are necessary. As shown in FIG. 12B,parallel arithmetic may often be performed in decoding processing. Inthe parallel arithmetic, the entropy decoding step S1410 where anarithmetic decoding is performed on the obtained bit stream according toa predetermined method (CABAC or CAVLC) (Step S1411) and a decodingparameter is obtained (Step S1412) is separately performed from thedecoding processing step (Step S1413) where a prediction image isgenerated based on a decoding parameter to obtain a decoding imagesignal. Here, decoding information necessary for the arithmetic decodingstep S1411 is obtained from the feedback of Step S1413.

The entropy decoding step S1410 needs to wait for the result of thedecoding processing step S1413, which does not allow high-speedcalculations. Therefore, reducing the feedback is particularly importantfor high-speed calculations.

As shown in FIG. 11, the image decoding apparatus according toEmbodiment 2 always calls the step for decoding the candidate predictionmode number (Step S1109) when the prediction mode use flag indicates 1(the signal decoded in the entropy decoding step) (YES in Step S1105);and thus, there is no need to wait for the completion of the decodingprocessing (Step S1413).

On the other hand, in the conventional syntax structure shown in FIG.6A, it is necessary to determine the number of the prediction modes(NumMPMCand). As described earlier, the target mode numbers of adjacentabove and left blocks need to be used for the determination. Thus, it isnecessary to wait for the completion of the decoding processing stepS1413. Therefore, the configuration according to the present disclosureincreases the processing speed of the decoding apparatus.

Variation of Embodiment 1 and Embodiment 2

(1) Each of the coding control unit 100 in FIG. 1 and the control unit210 in FIG. 10 is shown in relation with other processing unitsnecessary for explaining only inputs and outputs of information to andfrom the coding control unit 110 or the coding control unit 210.However, the coding control unit 110 and the control unit 210 may inputand output information necessary for other processing units vianot-shown signal lines. The coding control unit or the control unit maybe considered to be a controller for controlling the processing by eachof the processing units.

(2) Coding 34 target mode numbers have been described with an example of34 modes including 33 directions and one no-direction shown in FIG. 15.However, the same advantageous effects can be obtained even when thenumber of modes varies depending on the depth of the levels (L0 to L3)shown in FIG. 15.

For example, when the number of candidate intra prediction modes is (2to the power of n)+k, the coding mode number (rem_intra_luma_pred_mode)can be expressed in n bit or n+1 bit.

With the configuration of the decoding apparatus, the syntax structureshown in FIG. 6A and FIG. 6B can be properly decoded. Furthermore, asshown in FIG. 12B, in arithmetic decoding, the case where the number ofcandidate intra prediction modes is one is determined by simplyperforming the decoding processing. Therefore, there is no need toobtain adjacent target mode numbers for comparison. As a result,high-speed and accurate decoding can be performed with smaller memoryamount.

Embodiment 3

The processing described in each of embodiments can be simplyimplemented in an independent computer system, by recording, in arecording medium, a program for implementing the configurations of themoving picture coding method (image coding method) and the movingpicture decoding method (image decoding method) described in each ofembodiments. The recording media may be any recording media as long asthe program can be recorded, such as a magnetic disk, an optical disk, amagnetic optical disk, an IC card, and a semiconductor memory.

Hereinafter, the applications to the moving picture coding method (imagecoding method) and the moving picture decoding method (image decodingmethod) described in each of embodiments and systems using thereof willbe described. The system has a feature of having an image coding anddecoding apparatus that includes an image coding apparatus using theimage coding method and an image decoding apparatus using the imagedecoding method. Other configurations in the system can be changed asappropriate depending on the cases.

FIG. 16 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106, ex107, ex108, ex109, and ex110 which arefixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 16, and a combination inwhich any of the elements are connected is acceptable. In addition, eachdevice may be directly connected to the telephone network ex104, ratherthan via the base stations ex106 to ex110 which are the fixed wirelessstations. Furthermore, the devices may be interconnected to each othervia a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital camera, is capable ofcapturing both still images and video. Furthermore, the cellular phoneex114 may be the one that meets any of the standards such as GlobalSystem for Mobile Communications (GSM) (registered trademark), CodeDivision Multiple Access (CDMA), Wideband-Code Division Multiple Access(W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of images of alive show and others. In such a distribution, a content (for example,video of a music live show) captured by the user using the camera ex113is coded as described above in each of embodiments (i.e., the camerafunctions as the image coding apparatus according to an aspect of thepresent disclosure), and the coded content is transmitted to thestreaming server ex103. On the other hand, the streaming server ex103carries out stream distribution of the transmitted content data to theclients upon their requests. The clients include the computer ex111, thePDA ex112, the camera ex113, the cellular phone ex114, and the gamemachine ex115 that are capable of decoding the above-mentioned codeddata. Each of the devices that have received the distributed datadecodes and reproduces the coded data (i.e., functions as the imagedecoding apparatus according to an aspect of the present disclosure).

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding and decoding processes may be performed by anLSI ex500 generally included in each of the computer ex111 and thedevices. The LSI ex500 may be configured of a single chip or a pluralityof chips. Software for coding and decoding video may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, anda hard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.Furthermore, when the cellular phone ex114 is equipped with a camera,the video data obtained by the camera may be transmitted. The video datais data coded by the LSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients may receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the moving picture coding apparatus (image coding apparatus) andthe moving picture decoding apparatus (image decoding apparatus)described in each of embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 17. More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data coded bythe moving picture coding method described in each of embodiments (i.e.,data coded by the image coding apparatus according to an aspect of thepresent disclosure). Upon receipt of the multiplexed data, the broadcastsatellite ex202 transmits radio waves for broadcasting. Then, a home-useantenna ex204 with a satellite broadcast reception function receives theradio waves. Next, a device such as a television (receiver) ex300 and aset top box (STB) ex217 decodes the received multiplexed data, andreproduces the decoded data (i.e., functions as the image decodingapparatus according to an aspect of the present disclosure).

Furthermore, a reader/recorder ex218 (i) reads and decodes themultiplexed data recorded on a recording medium ex215, such as a DVD anda BD, or (i) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data. The reader/recorder ex218 can include the moving picturedecoding apparatus or the moving picture coding apparatus as shown ineach of embodiments. In this case, the reproduced video signals aredisplayed on the monitor ex219, and can be reproduced by another deviceor system using the recording medium ex215 on which the multiplexed datais recorded. It is also possible to implement the moving picturedecoding apparatus in the set top box ex217 connected to the cable ex203for a cable television or to the antenna ex204 for satellite and/orterrestrial broadcasting, so as to display the video signals on themonitor ex219 of the television ex300. The moving picture decodingapparatus may be implemented not in the set top box but in thetelevision ex300.

FIG. 18 illustrates the television (receiver) ex300 that uses the movingpicture coding method and the moving picture decoding method describedin each of embodiments. The television ex300 includes: a tuner ex301that obtains or provides multiplexed data obtained by multiplexing audiodata onto video data, through the antenna ex204 or the cable ex203, etc.that receives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 that decode audio data and video data and codeaudio data and video data, respectively (which function as the imagecoding apparatus and the image decoding apparatus according to theaspects of the present disclosure); and an output unit ex309 including aspeaker ex307 that provides the decoded audio signal, and a display unitex308 that displays the decoded video signal, such as a display.Furthermore, the television ex300 includes an interface unit ex317including an operation input unit ex312 that receives an input of a useroperation. Furthermore, the television ex300 includes a control unitex310 that controls overall each constituent element of the televisionex300, and a power supply circuit unit ex311 that supplies power to eachof the elements. Other than the operation input unit ex312, theinterface unit ex317 may include: a bridge ex313 that is connected to anexternal device, such as the reader/recorder ex218; a slot unit ex314for enabling attachment of the recording medium ex216, such as an SDcard; a driver ex315 to be connected to an external recording medium,such as a hard disk; and a modem ex316 to be connected to a telephonenetwork. Here, the recording medium ex216 can electrically recordinformation using a non-volatile/volatile semiconductor memory elementfor storage. The constituent elements of the television ex300 areconnected to each other through a synchronous bus.

First, the configuration in which the television ex300 decodesmultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon a user operation through a remote controllerex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside, respectively. When the output unit ex309 provides thevideo signal and the audio signal, the signals may be temporarily storedin buffers ex318 and ex319, and others so that the signals arereproduced in synchronization with each other. Furthermore, thetelevision ex300 may read multiplexed data not through a broadcast andothers but from the recording media ex215 and ex216, such as a magneticdisk, an optical disk, and a SD card. Next, a configuration in which thetelevision ex300 codes an audio signal and a video signal, and transmitsthe data outside or writes the data on a recording medium will bedescribed. In the television ex300, upon a user operation through theremote controller ex220 and others, the audio signal processing unitex304 codes an audio signal, and the video signal processing unit ex305codes a video signal, under control of the control unit ex310 using thecoding method described in each of embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in thebuffers ex320 and ex321, and others so that the signals are reproducedin synchronization with each other. Here, the buffers ex318, ex319,ex320, and ex321 may be plural as illustrated, or at least one buffermay be shared in the television ex300. Furthermore, data may be storedin a buffer so that the system overflow and underflow may be avoidedbetween the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be capable of only receiving, decoding, andproviding outside data but not the coding, multiplexing, and providingoutside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may decode or code the multiplexed data, and thetelevision ex300 and the reader/recorder ex218 may share the decoding orcoding.

As an example, FIG. 19 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or onan optical disk. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot in a recording surface of the recording medium ex215 thatis an optical disk to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. The disk motor ex405 rotates therecording medium ex215. The servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 20 illustrates the recording medium ex215 that is the optical disk.On the recording surface of the recording medium ex215, guide groovesare spirally formed, and an information track ex230 records, in advance,address information indicating an absolute position on the diskaccording to change in a shape of the guide grooves. The addressinformation includes information for determining positions of recordingblocks ex231 that are a unit for recording data. Reproducing theinformation track ex230 and reading the address information in anapparatus that records and reproduces data can lead to determination ofthe positions of the recording blocks. Furthermore, the recording mediumex215 includes a data recording area ex233, an inner circumference areaex232, and an outer circumference area ex234. The data recording areaex233 is an area for use in recording the user data. The innercircumference area ex232 and the outer circumference area ex234 that areinside and outside of the data recording area ex233, respectively arefor specific use except for recording the user data. The informationreproducing/recording unit 400 reads and writes coded audio, coded videodata, or multiplexed data obtained by multiplexing the coded audio andvideo data, from and on the data recording area ex233 of the recordingmedium ex215.

Although an optical disk having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disk is notlimited to such, and may be an optical disk having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disk may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disk and for recording information havingdifferent layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be a configuration, for example, includinga GPS receiving unit from the configuration illustrated in FIG. 18. Thesame will be true for the configuration of the computer ex111, thecellular phone ex114, and others.

FIG. 21A illustrates the cellular phone ex114 that uses the movingpicture coding method and the moving picture decoding method describedin embodiments. The cellular phone ex114 includes: an antenna ex350 fortransmitting and receiving radio waves through the base station ex110; acamera unit ex365 capable of capturing moving and still images; and adisplay unit ex358 such as a liquid crystal display for displaying thedata such as decoded video captured by the camera unit ex365 or receivedby the antenna ex350. The cellular phone ex114 further includes: a mainbody unit including an operation key unit ex366; an audio output unitex357 such as a speaker for output of audio; an audio input unit ex356such as a microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still pictures, e-mails, or others; and aslot unit ex364 that is an interface unit for a recording medium thatstores data in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 21B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keyunit ex366 is connected mutually, via a synchronous bus ex370, to apower supply circuit unit ex361, an operation input control unit ex362,a video signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex357.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation key unitex366 and others of the main body is sent out to the main control unitex360 via the operation input control unit ex362. The main control unitex360 causes the modulation/demodulation unit ex352 to perform spreadspectrum processing on the text data, and the transmitting and receivingunit ex351 performs the digital-to-analog conversion and the frequencyconversion on the resulting data to transmit the data to the basestation ex110 via the antenna ex350. When an e-mail is received,processing that is approximately inverse to the processing fortransmitting an e-mail is performed on the received data, and theresulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving picture coding method shown in each of embodiments (i.e.,functions as the image coding apparatus according to the aspect of thepresent disclosure), and transmits the coded video data to themultiplexing/demultiplexing unit ex353. In contrast, during when thecamera unit ex365 captures video, still images, and others, the audiosignal processing unit ex354 codes audio signals collected by the audioinput unit ex356, and transmits the coded audio data to themultiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the multiplexed data, and the transmitting and receivingunit ex351 performs digital-to-analog conversion and frequencyconversion on the data so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bit stream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using amoving picture decoding method corresponding to the moving picturecoding method shown in each of embodiments (i.e., functions as the imagedecoding apparatus according to the aspect of the present disclosure),and then the display unit ex357 displays, for instance, the video andstill images included in the video file linked to the Web page via theLCD control unit ex359. Furthermore, the audio signal processing unitex354 decodes the audio signal, and the audio output unit ex357 providesthe audio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 probably have 3 types of implementationconfigurations including not only (i) a transmitting and receivingterminal including both a coding apparatus and a decoding apparatus, butalso (ii) a transmitting terminal including only a coding apparatus and(iii) a receiving terminal including only a decoding apparatus. Althoughthe digital broadcasting system ex200 receives and transmits themultiplexed data obtained by multiplexing audio data onto video data inthe description, the multiplexed data may be data obtained bymultiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving picture coding method and the moving picturedecoding method in each of embodiments can be used in any of the devicesand systems described. Thus, the advantages described in each ofembodiments can be obtained.

Furthermore, the present disclosure is not limited to embodiments, andvarious modifications and revisions are possible without departing fromthe scope of the present disclosure.

Embodiment 4

Video data can be generated by switching, as necessary, between (i) themoving picture coding method or the moving picture coding apparatusshown in each of embodiments and (ii) a moving picture coding method ora moving picture coding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconform cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture coding method and by themoving picture coding apparatus shown in each of embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG-2 Transport Stream format.

FIG. 22 illustrates a structure of the multiplexed data. As illustratedin FIG. 22, the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of the movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the primary video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is coded in the moving picture coding method or by themoving picture coding apparatus shown in each of embodiments, or in amoving picture coding method or by a moving picture coding apparatus inconformity with a conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1. The audio stream is coded in accordance with a standard, such asDolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linear PCM. Eachstream included in the multiplexed data is identified by PID.

For example, 0x1011 is allocated to the video stream to be used forvideo of a movie, 0x1100 to 0x111F are allocated to the audio streams,0x1200 to 0x121F are allocated to the presentation graphics streams,0x1400 to 0x141F are allocated to the interactive graphics streams,0x1B00 to 0x1B1F are allocated to the video streams to be used forsecondary video of the movie, and 0x1A00 to 0x1A1F are allocated to theaudio streams to be used for the secondary audio to be mixed with theprimary audio.

FIG. 23 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 24 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 24 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 24, the video stream is divided into pictures as I pictures, Bpictures, and P pictures each of which is a video presentation unit, andthe pictures are stored in a payload of each of the PES packets. Each ofthe PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 25 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The source packets are arranged in the multiplexed dataas shown at the bottom of FIG. 25. The numbers incrementing from thehead of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 26 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 27. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 27, the multiplexed data information includes asystem rate, a reproduction start time, and a reproduction end time. Thesystem rate indicates the maximum transfer rate at which a system targetdecoder to be described later transfers the multiplexed data to a PIDfilter. The intervals of the ATSs included in the multiplexed data areset to not higher than a system rate. The reproduction start timeindicates a PTS in a video frame at the head of the multiplexed data. Aninterval of one frame is added to a PTS in a video frame at the end ofthe multiplexed data, and the PTS is set to the reproduction end time.

As shown in FIG. 28, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In the present embodiment, the multiplexed data to be used is of astream type included in the PMT. Furthermore, when the multiplexed datais recorded on a recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, the moving picture coding method or the moving picturecoding apparatus described in each of embodiments includes a step or aunit for allocating unique information indicating video data generatedby the moving picture coding method or the moving picture codingapparatus in each of embodiments, to the stream type included in the PMTor the video stream attribute information. With the configuration, thevideo data generated by the moving picture coding method or the movingpicture coding apparatus described in each of embodiments can bedistinguished from video data that conforms to another standard.

Furthermore, FIG. 29 illustrates steps of the moving picture decodingmethod according to the present embodiment. In Step exS100, the streamtype included in the PMT or the video stream attribute informationincluded in the multiplexed data information is obtained from themultiplexed data. Next, in Step exS101, it is determined whether or notthe stream type or the video stream attribute information indicates thatthe multiplexed data is generated by the moving picture coding method orthe moving picture coding apparatus in each of embodiments. When it isdetermined that the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving picture coding method or the moving picture coding apparatus ineach of embodiments, in Step exS102, decoding is performed by the movingpicture decoding method in each of embodiments. Furthermore, when thestream type or the video stream attribute information indicatesconformance to the conventional standards, such as MPEG-2, MPEG-4 AVC,and VC-1, in Step exS103, decoding is performed by a moving picturedecoding method in conformity with the conventional standards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving picture decoding method or the moving picture decoding apparatusthat is described in each of embodiments can perform decoding. Even whenmultiplexed data that conforms to a different standard is input, anappropriate decoding method or apparatus can be selected. Thus, itbecomes possible to decode information without any error. Furthermore,the moving picture coding method or apparatus, or the moving picturedecoding method or apparatus in the present embodiment can be used inthe devices and systems described above.

Embodiment 5

Each of the moving picture coding method, the moving picture codingapparatus, the moving picture decoding method, and the moving picturedecoding apparatus in each of embodiments is typically achieved in theform of an integrated circuit or a Large Scale Integrated (LSI) circuit.As an example of the LSI, FIG. 30 illustrates a configuration of the LSIex500 that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AVIO ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream I/O ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recordingmedium ex215. When data sets are multiplexed, the data should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present disclosureis applied to biotechnology.

Embodiment 6

When video data generated in the moving picture coding method or by themoving picture coding apparatus described in each of embodiments isdecoded, compared to when video data that conforms to a conventionalstandard, such as MPEG-2, MPEG-4 AVC, and VC-1 is decoded, theprocessing amount probably increases. Thus, the LSI ex500 needs to beset to a driving frequency higher than that of the CPU ex502 to be usedwhen video data in conformity with the conventional standard is decoded.However, when the driving frequency is set higher, there is a problemthat the power consumption increases.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 31illustrates a configuration ex800 in the present embodiment. A drivingfrequency switching unit ex803 sets a driving frequency to a higherdriving frequency when video data is generated by the moving picturecoding method or the moving picture coding apparatus described in eachof embodiments. Then, the driving frequency switching unit ex803instructs a decoding processing unit ex801 that executes the movingpicture decoding method described in each of embodiments to decode thevideo data. When the video data conforms to the conventional standard,the driving frequency switching unit ex803 sets a driving frequency to alower driving frequency than that of the video data generated by themoving picture coding method or the moving picture coding apparatusdescribed in each of embodiments. Then, the driving frequency switchingunit ex803 instructs the decoding processing unit ex802 that conforms tothe conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 30.Here, each of the decoding processing unit ex801 that executes themoving picture decoding method described in each of embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 30. TheCPU ex502 determines to which standard the video data conforms. Then,the driving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on the signal from the CPUex502. For example, the identification information described inEmbodiment 4 is probably used for identifying the video data. Theidentification information is not limited to the one described inEmbodiment 4 but may be any information as long as the informationindicates to which standard the video data conforms. For example, whenwhich standard video data conforms to can be determined based on anexternal signal for determining that the video data is used for atelevision or a disk, etc., the determination may be made based on suchan external signal. Furthermore, the CPU ex502 selects a drivingfrequency based on, for example, a look-up table in which the standardsof the video data are associated with the driving frequencies as shownin FIG. 33. The driving frequency can be selected by storing the look-uptable in the buffer ex508 and in an internal memory of an LSI, and withreference to the look-up table by the CPU ex502.

FIG. 32 illustrates steps for executing a method in the presentembodiment. First, in Step exS200, the signal processing unit ex507obtains identification information from the multiplexed data. Next, inStep exS201, the CPU ex502 determines whether or not the video data isgenerated by the coding method and the coding apparatus described ineach of embodiments, based on the identification information. When thevideo data is generated by the moving picture coding method and themoving picture coding apparatus described in each of embodiments, inStep exS202, the CPU ex502 transmits a signal for setting the drivingfrequency to a higher driving frequency to the driving frequency controlunit ex512. Then, the driving frequency control unit ex512 sets thedriving frequency to the higher driving frequency. On the other hand,when the identification information indicates that the video dataconforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1, in Step exS203, the CPU ex502 transmits a signal for setting thedriving frequency to a lower driving frequency to the driving frequencycontrol unit ex512. Then, the driving frequency control unit ex512 setsthe driving frequency to the lower driving frequency than that in thecase where the video data is generated by the moving picture codingmethod and the moving picture coding apparatus described in each ofembodiment.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the processing amount for decoding is larger, thedriving frequency may be set higher, and when the processing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when theprocessing amount for decoding video data in conformity with MPEG-4 AVCis larger than the processing amount for decoding video data generatedby the moving picture coding method and the moving picture codingapparatus described in each of embodiments, the driving frequency isprobably set in reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture coding method and the moving picturecoding apparatus described in each of embodiments, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set higher. When the identification information indicates thatthe video data conforms to the conventional standard, such as MPEG-2,MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or theapparatus including the LSI ex500 is probably set lower. As anotherexample, when the identification information indicates that the videodata is generated by the moving picture coding method and the movingpicture coding apparatus described in each of embodiments, the drivingof the CPU ex502 does not probably have to be suspended. When theidentification information indicates that the video data conforms to theconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the drivingof the CPU ex502 is probably suspended at a given time because the CPUex502 has extra processing capacity. Even when the identificationinformation indicates that the video data is generated by the movingpicture coding method and the moving picture coding apparatus describedin each of embodiments, in the case where the CPU ex502 has extraprocessing capacity, the driving of the CPU ex502 is probably suspendedat a given time. In such a case, the suspending time is probably setshorter than that in the case where when the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Embodiment 7

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a cellular phone. In order to enable decoding theplurality of video data that conforms to the different standards, thesignal processing unit ex507 of the LSI ex500 needs to conform to thedifferent standards. However, the problems of increase in the scale ofthe circuit of the LSI ex500 and increase in the cost arise with theindividual use of the signal processing units ex507 that conform to therespective standards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 34A showsan example of the configuration. For example, the moving picturedecoding method described in each of embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy coding, inverse quantization,deblocking filtering, and motion compensated prediction. The details ofprocessing to be shared probably include use of a decoding processingunit ex902 that conforms to MPEG-4 AVC. In contrast, a dedicateddecoding processing unit ex901 is probably used for other processingunique to an aspect of the present disclosure. The decoding processingunit for implementing the moving picture decoding method described ineach of embodiments may be shared for the processing to be shared, and adedicated decoding processing unit may be used for processing unique tothat of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 34B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to an aspect of the present disclosure, a dedicated decodingprocessing unit ex1002 that supports the processing unique to anotherconventional standard, and a decoding processing unit ex1003 thatsupports processing to be shared between the moving picture decodingmethod according to the aspect of the present disclosure and theconventional moving picture decoding method. Here, the dedicateddecoding processing units ex1001 and ex1002 are not necessarilyspecialized for the processing according to the aspect of the presentdisclosure and the processing of the conventional standard,respectively, and may be the ones capable of implementing generalprocessing. Furthermore, the configuration of the present embodiment canbe implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving picture decoding methodaccording to the aspect of the present disclosure and the moving picturedecoding method in conformity with the conventional standard.

INDUSTRIAL APPLICABILITY

The present disclosure relates to moving picture coding and decodingmethods. More specifically, the present disclosure relates to methods ofcoding and decoding mode numbers for differentiating methods ofgenerating intra prediction pixels in intra coding.

The invention claimed is:
 1. An image decoding apparatus of decoding, ona block-by-block basis, image data included in a coded stream, the imagedecoding apparatus comprising: a processor; and a non-transitorycomputer-readable medium storing thereon a computer program, which whenexecuted by the processor, causes the processor to perform operationsincluding: selecting candidates for an intra prediction mode to be usedfor intra prediction for a decoding target block from a plurality ofpredetermined intra prediction modes, each of the plurality ofpredetermined intra prediction modes having a mode number; deriving theselected candidates, the number of the candidates constantly being apredetermined fixed plural number, the predetermined fixed plural numberbeing at least 2 and less than a number of the plurality ofpredetermined intra prediction modes; making a candidates list whichincludes indices and the derived candidates, the derived candidatescorresponding on a one-to-one basis with the indices, and a number ofthe indices being equal to the predetermined fixed plural number;obtaining a coded flag which indicating whether the intra predictionmode is inferred from a neighboring block or not; decoding the codedflag to obtain a decoded flag; when the decoded flag indicates that theintra prediction mode is inferred from the neighboring block, (i)obtaining, from the coded stream, a coded specified index whichspecifies an index of one of the derived candidates as the intraprediction mode to be used for intra prediction for the decoding targetblock, (ii) decoding the coded specified index to obtain a decodedspecified index, (iii) determining the one of the derived candidatesusing the decoded specified index, the index of the one of the derivedcandidates being specified by the decoded specified index in thecandidates list, and (iv) decoding the image data using the determinedone of the derived candidates; and when the decoded flag indicates thatthe intra prediction mode is not inferred from the neighboring block,(i) obtaining a coded specified mode number from the coded stream, (ii)decoding the coded specified mode number to obtain a decoded specifiedmode number, and (iii) comparing the mode number of one of the derivedcandidates with the decoded specified mode number, when the mode numberof the one of the derived candidates is larger than the decodedspecified mode number, determining the one of the derived candidates asthe intra prediction mode to be used for intra prediction for thedecoding target block, and decoding the image data using the determinedone of the derived candidates, and when the mode number of the one ofthe derived candidates is smaller than or equal to the decoded specifiedmode number, adding one to the decoded specified mode number, anddecoding the image data using one of the plurality of predeterminedintra prediction modes which is specified by the number obtained byadding one to the decoded specified mode number, wherein the derivingincludes: deriving a first candidate for the intra prediction mode to beused for intra prediction for the decoding target block from an intraprediction mode used for intra prediction for each of adjacent blocksthat are adjacent to the decoding target block; and in a case that thenumber of the derived first candidates is smaller than the predeterminedfixed plural number, further deriving a second candidate as a DCprediction mode to be used for intra prediction and a third candidate asa vertical (angular) prediction mode to be used for intra prediction. 2.The image decoding apparatus according to claim 1, wherein the comparingincludes comparing each of the mode numbers of the derived candidatesfrom a smallest index to a maximum index with the decoded specifiednumber, the maximum index being equal to the predetermined fixed pluralnumber minus one, when the mode number of one of the derived candidatesis larger than the decoded specified mode number, determining the one ofthe derived candidates as the intra prediction mode to be used for intraprediction for the decoding target block, and decoding the image datausing the determined one of the derived candidates, and when the modenumber of one of the derived candidates is smaller than or equal to thedecoded specified mode number, (i) adding one to the decoded specifiedmode number, and adding one to the index, (ii) comparing the mode numberof one of the derived candidates corresponding to the number obtained byadding one to the index with the number obtained by adding one to thedecoded specified mode number, wherein the adding is repeated until thenumber obtained adding one to the index is equal to the maximum index orthe mode number of one of the derived candidates corresponding to thenumber obtained by adding one to the index is larger than the numberobtained by adding one to the decoded specified mode number, and (iii)decoding the image data using the one of the derived candidates which isspecified by the number obtained by adding one to specified mode numberor the one of the plurality of predetermined intra prediction modeswhich is specified by the number obtained by adding one to the index.